1. Field of the Invention
This invention generally relates to subsea drilling, and in particular to a system and method for unlatching and/or latching a rotating control device (RCD) or other oilfield device.
2. Description of Related Art
Marine risers extending from a wellhead fixed on the floor of an ocean have been used to circulate drilling fluid back to a structure or rig. An example of a marine riser and some of the associated drilling components is proposed in U.S. Pat. Nos. 4,626,135 and 7,258,171. RCDs have been proposed to be positioned with marine risers. U.S. Pat. No. 6,913,092 proposes a seal housing with a RCD positioned above sea level on the upper section of a marine riser to facilitate a mechanically controlled pressurized system. U.S. Pat. No. 7,237,623 proposes a method for drilling from a floating structure using an RCD positioned on a marine riser. U.S. Pat. Nos. 6,470,975; 7,159,669; and 7,258,171 propose positioning an RCD assembly in a housing disposed in a marine riser. In the '171 patent, the system for drilling in the floor of an ocean uses a RCD with a bearing assembly and a holding member for removably positioning the bearing assembly in a subsea housing. Also, an RCD has also been proposed in U.S. Pat. No. 6,138,774 to be positioned subsea without a marine riser.
More recently, the advantages of using underbalanced drilling, particularly in mature geological deepwater environments, have become known. RCD's, such as disclosed in U.S. Pat. No. 5,662,181, have provided a dependable seal between a rotating pipe and the riser while drilling operations are being conducted. U.S. Pat. No. 6,138,774 proposes the use of a RCD for overbalanced drilling of a borehole through subsea geological formations. U.S. Pat. No. 6,263,982 proposes an underbalanced drilling concept of using a RCD to seal a marine riser while drilling in the floor of an ocean from a floating structure. Additionally, U.S. Provisional Application No. 60/122,350, filed Mar. 2, 1999, entitled “Concepts for the Application of Rotating Control Head Technology to Deepwater Drilling Operations” proposes use of a RCD in deepwater drilling. U.S. Pat. No. 4,813,495 proposes a subsea RCD as an alternative to the conventional drilling system and method when used in conjunction with a subsea pump that returns the drilling fluid to a drilling vessel.
Conventional RCD assemblies have been sealed with a subsea housing active sealing mechanisms in the subsea housing. Pub. No. US 2010/0175882 proposes a mechanically extrudable seal or a hydraulically expanded seal to seal the RCD with the riser. Additionally, conventional RCD assemblies, such as proposed by U.S. Pat. No. 6,230,824, have used powered latching mechanisms in the subsea housing to position the RCD. U.S. Pat. No. 7,487,837 proposes a latch assembly for use with a riser for positioning an RCD. U.S. Pat. No. 7,836,946 B2 proposes a latching system to latch an RCD to a housing and active seals. U.S. Pat. No. 7,926,593 proposes a docking station housing positioned above the surface of the water for latching with an RCD. Pub. No. US 2009/0139724 proposes a latch position indicator system for remotely determining whether a latch assembly is latched or unlatched.
U.S. Pat. No. 6,129,152 proposes a flexible rotating bladder and seal assembly that is hydraulically latchable with its rotating blow-out preventer housing. U.S. Pat. No. 6,457,529 proposes a circumferential ring that forces dogs outward to releasably attach an RCD with a manifold. U.S. Pat. No. 7,040,394 proposes inflatable bladders/seals. U.S. Pat. No. 7,080,685 proposes a rotatable packer that may be latchingly removed independently of the bearings and other non-rotating portions of the RCD. The '685 patent also proposes the use of an indicator pin urged by a piston to indicate the position of the piston.
Latching assemblies for RCDs have been proposed to be operated subsea with an electro-hydraulic umbilical line from the surface. A remotely operated vehicle (ROV) and a human diver have also been proposed to operate the latching assemblies. However, an umbilical line may become damaged. It is also possible for sea depths and/or conditions to be unsafe and/or impractical for a diver or a ROV. In such situations, the marine riser may have to be removed to extract the RCD.
U.S. Pat. No. 3,405,387 proposes an acoustical control apparatus for controlling the operation of underwater valve equipment from the surface. U.S. Pat. No. 4,065,747 proposes an apparatus for transmitting command or control signals to underwater equipment. U.S. Pat. No. 7,123,162 proposes a subsea communication system for communicating with an apparatus at the seabed. Pub. No. US 2007/0173957 proposes a modular cable unit positioned subsea for the attachment of devices such as sensors and motors.
The above discussed U.S. Pat. Nos. 3,405,387; 4,065,747; 4,626,135; 4,813,495; 5,662,181; 6,129,152; 6,138,774; 6,230,824; 6,263,982; 6,457,529; 6,470,975; 6,913,092; 7,040,394; 7,080,685; 7,123,162; 7,159,669; 7,237,623; 7,258,171; 7,487,837; 7,836,946 B2; and 7,926,593 and Pub. Nos. US 2007/0173957; 2009/0139724; and 2010/0175882; and U.S. Provisional Application No. 60/122,350, filed Mar. 2, 1999, entitled “Concepts for the Application of Rotating Control Head Technology to Deepwater Drilling Operations” are all hereby incorporated by reference for all purposes in their entirety.
It would be desirable to have a system and method to unlatch an RCD or other oilfield device from a subsea latching assembly when the umbilical line primarily responsible for operating the latching assembly is damaged or use of the umbilical line is impractical or not desirable, and using a diver or an ROV may be unsafe or impractical.